What a spore print is
A mature mushroom cap drops millions of spores from its gills, pores or teeth. Set the cap on a surface and leave it, and the spores fall in a pattern that mirrors the underside of the cap. That pattern is a spore print. It is both a sample of the spores and a visual record of their colour and the shape of the gills.
A print is the oldest tool in the mycologist's kit. It needs no equipment, no power and no sterile technique to make, and it stores for years. Vendors on Culture Cave sell prints from gourmet species for microscopy, taxonomy and reference, listed under spore prints and swabs.
How to take a spore print from a gourmet mushroom
Any fresh cap with a fully opened gill surface will print. Oyster, shiitake, portobello and chestnut all work well. Lion's mane prints poorly because its spores drop from hanging teeth and the fruit body is irregular, so it is more often swabbed than printed.
- Pick a mature cap and cut the stem off flush with the gills. Do not wash it.
- Lay a square of clean aluminium foil, glass or card on a flat surface. For microscopy, foil or glass is better than paper because it gives a clean, dry release later. Wipe it with alcohol if you want a cleaner print.
- Place the cap gills down on the surface. A drop of water on top of the cap helps release.
- Cover the cap with a glass or bowl to stop air currents and keep humidity up.
- Leave it for 6 to 24 hours. Thick-fleshed caps and dry rooms need longer.
- Lift the cap straight up. Let the print air dry for an hour or two, uncovered, somewhere still. Then fold the foil over it or cover it with a second square, and label it.
A print taken this way is not sterile. It has been exposed to room air and to whatever was on the cap. That is fine for identification and microscopy, and it is the reason vendors who sell prints for research take theirs in front of a flow hood on sterilised foil.
Spore colour as an identification tool
Spore colour is one of the first characters used to place a mushroom in a genus. It is often more reliable than cap colour, which changes with age, weather and light. The main groups are these.
- White to cream. Oyster mushrooms (the print is often faintly lilac-grey), lion's mane, shiitake, enoki, and many Amanita and Russula species.
- Brown. Chocolate brown in Agaricus, which includes button and portobello. Rusty or cinnamon brown in Pholiota, which includes chestnut mushroom, and in Cortinarius.
- Purple-brown to purple-black. Stropharia, including the wine cap, and its relatives.
- Black. Ink caps, in Coprinus and Coprinellus.
- Pink to salmon. Pluteus, Volvariella (the paddy straw mushroom) and Entoloma.
Spore colour is read from a thick print on white paper for dark spores and on black paper or glass for pale ones. It narrows a field guide from hundreds of options to a handful. Under a microscope, spore size, shape and surface texture then narrow it further. The strain library notes spore colour for the species listed on Culture Cave.
Why mycologists keep prints on file
A print is a permanent voucher. Herbaria and research collections keep prints alongside dried specimens because the spores can be rehydrated and examined decades later. For a hobbyist, the reasons are the same on a smaller scale.
- A print records exactly which fruit body a culture came from, so a strain can be traced back.
- Spores are genetically diverse, so a print holds far more variation than any single isolate. If a cultivated gourmet strain weakens over years of transfers, the print is the reserve.
- Prints take almost no space, need no refrigeration, and last for years.
- Comparing prints side by side is the fastest way to check that two mushrooms are the same species.
Spore swabs: the sterile alternative
A spore swab is a sterile cotton bud rolled across the gills of a fresh mushroom, then sealed back into its wrapper. It picks up spores without needing the cap to sit for hours, and it can be done in front of a flow hood so the sample stays clean.
Swabs are the usual format for species that print badly, such as lion's mane and other toothed fungi, and for small or thin caps that would dry out before dropping a print. They are also easier to post. The disadvantage is that a swab carries far fewer spores than a thick print, and you cannot read spore colour from it. For taxonomy and microscopy, a swab is often enough. For a reference file, a print is better. Both are grouped together under spore prints and swabs.
Storing prints
Spores are tough but not immortal. Four things shorten their life: moisture, light, heat and air. Store prints to avoid all four.
- Dry. Let the print dry fully before sealing. A damp print grows mould.
- Dark. Ultraviolet light damages spores. Keep prints in an envelope inside a box or drawer.
- Cool. Room temperature is fine. A fridge is better for long-term storage, but let the sealed packet come to room temperature before opening to avoid condensation.
- Sealed. Fold the foil, put it in a zip bag, and squeeze the air out. Some people add a silica gel sachet.
- Dated. Write the species, source and date on the packet. A print with no date is a print of unknown value.
Stored this way, prints of most species stay useful for microscopy for several years. The spore syringe storage guide covers the equivalent for liquid samples.
From print to syringe for microscopy
Most spore syringes start as prints. In general terms, a vendor scrapes a small amount of the print into sterile water in a sterile container, mixes it so the spores disperse, and draws the suspension into syringes. The work is done in front of a flow hood, and the water is sterilised in a pressure cooker beforehand. A single good print can produce many syringes.
For the researcher, the syringe is convenience. A drop on a slide, a cover slip, and the spores are ready to measure and photograph. The microscopy guide walks through that. The print is the source, and some researchers prefer to buy the print and make their own slides directly from it, because a print has not been diluted and lets them see the spores in bulk.
How to read vendor labels
A good print label gives you the species and strain name, the date the print was taken, the vendor's name, and often the substrate or origin of the fruit body. Some vendors add a batch number and a note on whether the print was taken under a flow hood. Look for a date within the last year or two. Be cautious of labels with a species name only, no date and no source.
On Culture Cave, every listing shows the vendor's country, where they ship, and reviews from people who have bought from them. The vendor guide explains what the reviews tell you and what to ask before ordering.
Prints or syringes: which to buy
Buy a print when you want a reference specimen, want to see spore colour, plan to keep the sample for years, or want to make your own slides from an undiluted source. Buy a syringe when you want a sample ready to go under the microscope with no preparation. Syringes are easier to use but have a shorter shelf life. The isolated vs multispore guide and the spore syringes category cover what is on offer.
If you want to grow gourmet mushrooms rather than study them, neither is the right starting point. A liquid culture or a colonised agar plate is faster and far more predictable, and spore syringe vs liquid culture explains why.